Effects on Pig Behavior, Stress and Carcass Characteristics of a Short-term Diet with High Levels of L-tryptophan

Abstract

Tryptophan plays an important role as the immediate precursor of serotonin synthesis. The serotoninactivity in the brain has been implicated in the regulation of behavioral and physiological processes suchas mood, aggression, susceptibility to stress, sleep patterns and feed intake. The pig production systemsof today emphasize concern with the animal’s well-being and welfare. Therefore, a high supplemental Ltryptophan,through its ability to increase serotonin, may reduce stress and improve performance and porkquality. However, there is no information available for pig farms in Thailand of supplemental L-tryptophan’seffect on behaviors, stress and pork quality. This work determined how three levels of dietary tryptophan,starting with the standard requirement for growth (control), going to twice (2×), and finally 4 times (4×) thecontrol amount, affected the general and aggressive behaviors, and stress in pigs and also pork quality. Theresults found no difference in general behavior of pigs between the treatments. The aggressive behaviorsof pigs also expressed no significant difference between the treatments. However, biting behavior was thelowest at the 4× supplemental diet. Salivary cortisol levels indicated high stress in the pigs during regroupingand transportation. Carcass temperature 45 min postmortem was the highest at the standard level tryptophandiet. These results give the evidence that a short-term supplementation of four times the requirement forgrowth of L-tryptophan in a diet in pigs can reduce stress during regrouping and transporting and improvemeat quality after slaughter.

Keywords : Serotonin / Cortisol / Welfare / Pork